DANBURY — City school officials are examining safety procedures as they investigate a complaint by a mother of a kindergarten student who said her 5-year-old son left school alone and unnoticed last week.

The child’s mother, Allison Solis, said the boy’s grandmother spotted him riding his bike as she walked to South Street School to pick him up around 3 p.m. Thursday. Dismissal time at the school is 3:30 p.m.

Solis filed a complaint with the school district on Friday and kept her son home on Monday.

“I just need to know that I can be comfortable with him being at the school,” she said. “Right now, I’m not — not until a plan is put in place.”

Kim Thompson, human resources director for Danbury Public Schools, said the district was “mid-process” in its investigation on Monday.

“Safety is our primary concern right now,” Thompson said. “We’re sifting through what we know and going through our processes. If something goes wrong, we want to find out what happened and fix it.”

The district is also evaluating its procedures and “working with staff to make sure everything is being followed,” she said.

Thompson said she doesn’t know how long it will take to complete the investigation. She said reviewing school procedures is “a constant process” and the district is “always looking to tune up [its] processes.”

Making sure safety procedures are followed isn’t enough, Solis said Friday.

“I want all the teachers — not just at South Street, but at all the elementary schools in Danbury — to understand that it’s not OK to not know where students are,” she said. “If it takes retraining, so be it. This should not have happened.”

Solis met with school staff, Principal Carmen Vargas-Guevara and the assistant superintendent Monday afternoon to discuss her complaint.

Solis said she wasn’t going into the meeting looking for answers.

“It’s more about what [the schools] are going to do now,” she said.